The compound deoxybiotinyl hexamethylenediamine-DOTA has been described in international patent application WO 02066075 under the name of the Applicant. DOTA is 1,4,7,10-tetraazacyclododecanotetra-acetic acid (1,4,7,10-tetraazacyclododecanetetra-acetic acid).
The structural formula of deoxybiotinyl hexamethylenediamine-DOTA is reported here for completeness.

The process for synthesising this product is also described in the same patent application WO 02066075 and also reported in the example on page 15 of the above-mentioned application. The compound reported here as ST2210 corresponds to compound 4 of the Example of WO 02066075. In particular the intermediate product biotinyl hexamethylenediamine hydrochloride (ST2551 or compound 3 of the example of WO 02066075), was obtained with preparatory chromatography with a yield of 55% and an undefined titre.
The final deoxybiotinyl hexamethylenediamine-DOTA product (ST2210 or compound 4 of the example of WO 02066075), was obtained by condensing ST2551 with DOTA as illustrated in diagram 1.

The reaction conducted in this way produced low synthetic yields (the presence in DOTA of four unprotected carboxylic functionality equivalents, involved the formation of various by-products) and problems with purification. Indeed to obtain the end product it was necessary to use HPLC on a preparatory scale with a yield of 20%.